The Nervous System & The Brain: The Basic Structure

The Nervous System & The Brain: The Basic Structure Psychology 12

Have you ever experienced a runners high? It’s almost like running is this great friend we both share…Anyways, that’s what I’d like to talk to you about…running as a friend, a companion…in other words, the relationship of running. “WHAT!?” many of you will be saying, “I thought that I was going to learn about how to improve my 10k time.” Go read “Runner’s World” for that. You see, I don’t view running as what I DO or what I AM, but as this thing, this force, that changes me over time… ---from “Running and Me: A Love Story” by Joan Nesbit, 1999

Runner’s High Why does the writer love running so much? One of the reasons may be that people who do a lot of running—especially long-distance running, often talk of an effect called a “runner’s high.” The longer they run, the more tired they get, of course; but at some point, the runners will “push through the wall” and “get their second wind.” Why does this happen? Endorphins, which are neurotransmitters, produce the euphoria of a runner’s high. As the body deals with a very physically stressful situation—running---the runner’s body reacts to stress.

Question for Discussion… What other types of physically stressful situations may the human body encounter? How does the nervous system react?

How the Nervous System Works The nervous system controls your emotions, movements, thinking and behaviour. Structurally, it is divided into two parts—the central nervous system [CNS] ( the brain and the spinal cord) and the peripheral nervous system [PNS] (the smaller branches of nerves that reach the other parts of the body.

How the Nervous System Works All parts of the nervous system are protected: the brain by the skull and several layers of sheathing, the spinal cord by the vertebrae, and the peripheral nerves by layers of sheathing. The bony protection of the spinal cord is vital. An injury to the spinal cord could prevent the transmittal of messages between the brain and the muscles, and could result in paralysis.

Neurons Messages to and from the brain travel along nerves, which are strings of long, thin cells called NEURONS. Chemical-electrical signals travel down the neurons much as a flame travels along a firecracker fuse. The main difference is that the neuron can fire (burn) over and over again, hundreds of times a minute. Transmission between the neurons, or nerve cells, occur whenever the cells are stimulated—the neuron fires according to the all-or-none principle (when it fires, it fires at full strength).

The Neuron Connection The space between neurons is called the SYNAPSE. The synapse is a junction or connection between the neurons. A neuron transmits its impulse or message to another neuron across the synapse by releasing chemicals called NEUROTRANSMITTERS. These neurotransmitters open chemical locks or excite receptors Neurons do not touch each other—a neuron sends a message across a gap called a synapse by releasing a neurotransmitter. These neurotransmitters are received by the dendrite of another neuron. FYI [the synapse is less than one millionth of an inch wide and is filled with fluid that transmits the chemical from one neuron to another]

Neurotransmitters There are many types of neurotransmitters; for example, Norepinephrine: involved in learning and memory Endorphin: inhibits pain Acetylcholine: movement and memory. An undersupply is associated with paralysis and Alzheimer’s disease Dopamine:Learning, emotional arousal and movement. An oversupply is linked to schizophrenia—an undersupply is linked to Parkinson’s disease Serotonin:cognitive functions—memory and learning. It also regulates intestinal movements and mood, appetite, sleep, as well as muscle contraction. An undersupply of serotonin and norepinephrine may result in depression

Learning Activity Complete questions 1-5 on page 159.

A Tour of the Brain We begin our exploration of the brain at the lower end, where the spinal cord joins the base of the brain, and then continue upward toward the skull. Note that as we move from bottom to top, “lower,” basic processes like breathing generally give way to “higher,” more complex mental processes.

Tour of the Brain The brain is the control center of the body. Made up of dense "grey matter" consisting of complicated networks of interconnected neurons, the brain can be superficially divided into three main parts: the hindbrain, the midbrain and the forebrain.

Tour of the Brain • The brain can be divided into THREE major sections: the hindbrain,midbrain,andforebrain. • Also, the large section labeled as the BRAINSTEM includes parts of all three of these3 sections and helps regulate reflex activities important to survival (ie, heartbeat and respiration)

Tour of the Brain • Throughout the tour, note that certain brain structures are specialized to perform certain tasks, a process known as localization of function, but also note that most parts of the brain are not so specialized—they perform overlapping functions.

Tour of the Brain: The Hindbrain • Have you ever wondered what allows you to automatically breathe and your heart to keep pumping—automatic behaviours and survival responses like these are either controlled by or influenced by parts of your hindbrain, which includes the medulla, pons and cerebellum.

Tour of the Brain: The Hindbrain • Medulla: Essentially is an extension of the spinal cord, with many nerve fibers passing through it carrying information to an from the brain. It also controls many essential automatic brain functions like respiration and heartbeat.

Tour of the Brain: The Hindbrain • Cerebellum: (“little brain”) is evolutionarily, a very old structure. It coordinates fine muscle movement and balance. The cerebellum coordinates the muscles so that movement is smooth and precise. It is also crucial for our sense of balance and equilibrium

Tour of the Brain: The Hindbrain • Pons: Located above the cerebellum and medulla, is involved in respiration, movement, sleeping, waking, and dreaming (among other things). It also contains many axons that cross from one side to the other (pons is Latin for “bridge”)

Tour of the Brain: The Midbrain • The midbrain is the small part of the brain that helps orient our eye and body movements to visual and auditory stimuli, and works with the pons to help control sleep and level of arousal. It also contains a small structure involved with the neurotransmitter dopamine, while deteriorates in Parkinson’s disease.

Tour of the Brain: The Midbrain • Running through the core of the hindbrain, midbrain, and brainstem is the reticular (netlike) formation (RF). This finger-shaped network of neurons filters incoming sensory information and alerts the higher brain centers to important events. Without your RF, you would not be alert or perhaps even conscious. In fact, some general anesthics target the RF so pain sensations never register in the brain.

Tour of the Brain: The Forebrain • The Forebrain is the largest and most prominent part of the human brain. It includes the thalamus, hypothalamus, limbic system, and cerebral cortex. • The first three structures are located near the top of the brainstem. Wrapped around them is the cerebral cortex (cerebrum is Latin for “brain,” and cortex is Latin for “covering”)

Tour of the Brain: The Forebrain • Thalamus: Resembling two little footballs jointed side by side, the thalamus serves the major sensory relay center for the brain. Like an air traffic control centre that receives information from all aircraft and then directs them to the appropriate landing or takeoff areas, the thalamus receives input from nearly all the sensory systems and then directs this information to the appropriate areas. • For example, while you are reading this, your thalamus sends incoming visual signals to the visual area of your cortex. While listening to music, the information is transferred to the auditory area of the cortex.

Tour of the Brain: The Forebrain • Thalamus: In addition to relaying sensory information to the cortex it also integrates information from various senses and maybe involved in learning and memory. Injury to the thalamus can cause deafness, blindness, or loss of any other sense (except smell). Damage may cause the cortex to misinterpret or not receive vital sensory info. Interestingly, brain-imaging research links thalamus abnormalities to schizophrenia (a serious psychological disorder involving problems with sensory filtering and perception). Thalamus: Integrates input from the senses

Tour of the Brain: The Forebrain • Hypothalamus: Beneath the thalamus lies the hypothalamus (“hypo” meaning “under”). Although no larger than a kidney bean, it has been called the master control centre” for basic drives such as hunger, thirst, sex, and aggression. It also helps govern hormonal processes by regulating the endocrine system. Hanging down from the hypothalamus, the pituitary gland is considered the key endocrine gland because it releases hormones that activate the other endocrine glands. • The endocrine system is a system of glands, each of which secretes a type of hormone into the bloodstream to regulate the body. Hypothalamus: Controls basic drives, such as hunger

Tour of the Brain: The Forebrain • Limbic System: An interconnected group of forebrain structures, known as the limbic system, is located roughly along the border between the cerebral cortex and the lower-level brain structures (hence the term “limbic,” which means “edge” or “border”). Structures include the hippocampus, amygdala, thalamus, hypothalamus. • Responsible for emotions, drives, and memory, and involved in forming and retrieving memories. Limbic System: Regulates fear and other emotions

Tour of the Brain: The Forebrain • Limbic System: The major focus of interest in the limbic system, and particularly the amygdala, has been its production and regulation of emotions (e.g.. aggression and fear) • Also known for its role in pleasure or reward. A study done with rats—stimulating certain areas of the limbic system—cause a ”pleasure” response. The feeling was so rewarding that he rats would cross electrified grids, swim through water (which they normally avoid), and press a lever thousands of times until they collapsed from exhaustion—just to have this area of their brains stimulated. Limbic System: Regulates fear and other emotions

Tour of the Brain: The Forebrain • Cerebral Cortex: The centre for “higher” processing. • The gray, wrinkled cerebral cortex is responsible for most complex behaviours and higher mental processes. It plays such a vital role in human life that may consider it the essence of life. Without a functioning cortex, we would be almost completely unaware of ourselves and our surroundings. Cerebral Cortex: Governs higher mental processes, such as thinking

Tour of the Brain: The Forebrain • Cerebral Cortex: Convolutions • Although it is only about • ¼ inch thick, it is made up of approximately 30 billion neurons and nine times as many supporting cells. When spread out, the cortex would cover an area almost the size of a standard newspaper page. • How does your cortex, along with all your brain structures fit inside your skull? Imagine crumpling and rolling a newspaper sheet into a ball—you would retain the same surface area, but in a much smaller space. The cortex contains “wrinkles” called “convolutions” allowing it to hold billions of neurons in the restricted space of the skull.

Tour of the Brain: The Forebrain • Cerebral Cortex: Hemispheres • If you’ve ever watch brain surgery on TV—once the skull has been opened, you’ll first see a gray, wrinkled, cerebral cortex that closely resembles an oversized walnut. Like a walnut, the cortex has a similar division (fissure) down the centre, which marks the left and right hemispheres of the brain. They hemispheres are connected by a band of fibers called the corpus callosum. The two hemispheres make up about 80% of the brain’s weight and they are mostly filled with axon connections between the cortex and other brain structures. Each hemisphere controls the opposite side of the body

Cerebral Cortex: Hemispheres & Lobes of the Brain • The two cerebral hemispheres are divided into eight distinct areas, or lobes—four in each hemisphere. Like the lower-level brain structures, each lobe specializes in somewhat different tasks—another example of localization of function. However, some functions overlap between lobes.

Tour of the Brain: The Forebrain • Cerebral Cortex: Lobes • Frontal Lobe: Receives and coordinates messages from other lobes; motor control, speech production, and higher functions. Includes the motor cortex which controls voluntary movements and Broca’s area which controls speech production • Parietal Lobe: Receives information about pressure, pain, touch, and temperature. Includes the Somatosensory cortex which receives sensory messages. • Occipital Lobe: visual perception and vision—includes the Visual cortex that receives and processes visual information • Temporal Lobe: Hearing, language, comprehension, memory, and some emotional control—includes Wernicke’s area that controls language comprehension

Tour of the Brain: The Forebrain • Cerebral Cortex: Frontal Lobes The largest of the lobes, the two frontal lobes are located at the top front portion of the brain hemispheres—right behind your forehead. They receive and coordinate messages from all other lobes, while also being responsible for at least 3 other functions: 1. Higher functions—functions that distinguish us from other animals, such as thinking, personality, emotion, and memory. Damage to the frontal lobes affect motivation, drives, creativity, self-awareness, initiative, reasoning, and emotional behaviour. Abnormalities in FL are often observed in patients with schizophrenia

Tour of the Brain: The Forebrain • Cerebral Cortex: Frontal Lobes 2. Speech Production: In the left frontal lobe, on the surface of the cortex near the bottom of the motor control area lies Broca’s area, which is known to play a crucial role in speech production. 3. Motor Control: At the very back of the frontal lobes lies the motor cortex, which sends messages to the various muscles that instigate voluntary movement. When you call a friend on a cell phone, the motor control area of your frontal lobes guides your fingers to press the desired sequence of numbers.

Tour of the Brain: The Forebrain • Cerebral Cortex: Parietal Lobes At the top of the brain, just behind the frontal lobes, are the two parietal lobes. They contain the somatosensory cortex, which interpret bodily sensations including pressure, pain, touch, temperature, and location of body parts. When you step on a sharp nail, you quickly (and reflexively) withdraw your foot because the messages travel directly to and from your spinal cord. However, you do not experience “pain” until the neural messages reach the parietal lobes of the brain.

Tour of the Brain: The Forebrain • Cerebral Cortex: Temporal Lobes The two temporal lobes (Latin for “pertaining to the temples”)are responsible for auditory perception (hearing), language comprehension, memory, and some emotional control. The auditory cortex (which processes sound) is located at the top front of each temporal lobe. This area processes incoming sensory information from the ears and sends it to the parietal lobes, where it is combined with visual and other sensory info. In the LEFT temporal lobe, Wernicke’s area is involved in language comprehension.

Tour of the Brain: The Forebrain • Cerebral Cortex: Occipital Lobes (Latin “oh,” “in the back of,” and “caput,” “head”)—located at the lower back of the brain. Occipital lobes are responsible for vision and visual perception. Damage to this area can produce blindness, even though the eyes and their neural connection to the brain are perfectly healthy. The occipital lobes are involved in shape, colour, motion, and perception.

Split-Brain Research • Split-Brain Surgery: Cutting of the corpus callosum to separate the brain’s two hemispheres. When used medically to treat severe epilepsy, split-brain patients provide data on the functions of the two hemispheres. • This information has profoundly improved our understanding of how the two halves of the brain function.

Split-Brain Research • Hemispheric Specialization: although complex activities occur in both hemispheres, specialization of function occurs in some areas Right Hemisphere • Nonverbal Abilities: Music, art, perceptual and spatiomanipulative skills, recognition of faces, patterns and melodies, some language comprehension • Emotions: Associated with negative emotions, emotion expression, and emotion perception • Synthetic: figures things out by combining to form wholes • Controls and senses the left side of the body. • Left Hemisphere: • Language Functions: speaking, reading, writing, and understanding language • Emotions:Associated with positive emotions • Analytical:Figures things out step by step • Controls and senses the right side of the body

Traumatic Brain Injuries • Imagine yourself as a high school football player (not too difficult for some!). If you suffered a concussion while playing a game, would you tell your coach?

Traumatic Brain Injuries There is mounting evidence linking multiple concussions with permanent (and possibly fatal) brain damage… • According to a report, “many of the 1.2 million teenagers who play high school football either don’t know what a concussion is or they simply don’t care. They continue to play on and get hurt much worse—sometimes fatally.”

Traumatic Brain Injuries Millions of people suffer head injuries each year, and most of these injuries are minor—thanks to the bony skull’s protection for the brain. This is not the case for traumatic brain injuries (TBI). TBI is defined as an injury to the brain caused by significant trauma Symptoms: (range from mild to severe): headache, loss of consciousness, convulsions, coma and death. Two most common brain injuries are concussions (result from significant blow to the head) and contusions (bruises to the brain). Either TBI can result in prolonged or nonreversible brain damage and serious problems, such as extreme changes in personality, significant loss of motor skills, emotional control, and mental abilities

The Brain A) Questions: Answer questions 3, 4 & 5 on page 168. B) Read the Case Study on page 169 Answer the following questions: • How does split-brain surgery benefit both the patient and humans in general? Should split-brain surgery ever be performed on a person with no brain disorders? • Complete questions 1-3 from the case study.

The “Model” Brain • Objective: To gain a better understanding of the location and function of the parts of the brain • Let’s work with our right hemispheric spatiomanipulativeskills—we are going to build a 3-D version of the brain. Using your textbook, the slides and the chart you created yesterday as guides, create a 3-D cross section of the left side of the brain, making sure to include all the structures listed in your charts (obviously, none from the right hemisphere) Use a numbering system on the appropriate sections of the brain (attached with sticky notes & toothpicks) and write the corresponding names of the structures and their functions on card stock (recipe cards)..

Cross-section of the Brain

Time Reports: Lots of Action in the Memory Game • Read the Time article on page 180-1. • Answer the Analyzing the Article Questions 1-2

The Nervous System & The Brain: The Basic Structure